Thread: input redirection <

I wrote a standard i/o program which was taken from "c for dummies"

Code:

#include <stdio.h>

int main()

{
	char ch;	
	
	while ((ch = fgetc(stdin)) != EOF)
		fputc(ch,stdout);

	return(0);
}

I saved it as io.c and ran the program

Also, I created a new text file called text.txt and wrote the words

Code:

Hello. I am a text file

However, when I want to redirect stdin with

Code:

io < text.txt,

bash says that command io is not found.

Any ideas on how to resolve this?
I tried cat < text.txt and it works fine.

But a few pages later another command is shown ls -l | underline where underline is a program that I created, and again it shows that udnerline command is not found

Originally Posted by manasij7479

As the executable is in the current directory, you have to give "./io <text.txt"

That assumes the current working directory is not included in the path (the "./" is optional if it is). Which, admittedly, is good practice for several reasons.

Code:

char ch;   
     
while ((ch = fgetc(stdin)) != EOF)

The fgetc function returns an int, not a char. This can be important when comparing against EOF.

Originally Posted by hk_mp5kpdw

The fgetc function returns an int, not a char. This can be important when comparing against EOF.

It is important when comparing against EOF, as EOF is generally an integral value that cannot be represented by a char. So no char can test equal to EOF.

Originally Posted by grumpy

It is important when comparing against EOF, as EOF is generally an integral value that cannot be represented by a char. So no char can test equal to EOF.

If char is signed, it is certainly possible that a char can test equal to EOF, e.g., if EOF is -1. In such a case, the code that uses char may appear to be correct, but then fail when compiled elsewhere.